In conventional magnetic head systems, the magnetic head consists of an electromagnetic arrangement for writing, reading or erasing data on a magnetizable storage medium, movable relative thereto, such as a magnetic disk. Known kinds of magnetic head arrangements include ring electromagnets with an air gap, Hall effect components, magneto-resistive components and inductive electromagnetic arrangements. Typically, for use with a magnetic disk, the magnetic head is attached to a slider and lies opposite the disk surface.
Rotating magnetic disks of the type in which the magnetic head is in contact with the disk surface when the disk is at rest and flies above the disk surface when the disk is rotating at its operating speed are well known in the field. In such types of rotating magnetic disks, the magnetic head, which is supported on a slider, rides on a cushion or bearing of air above the disk surface when the disk is rotating at its operating speed. The slider is movable radially on the disk to be positioned over a selected one of a group of concentric recording tracks. The slider is carried on a suspension assembly connected ultimately to an actuator. The slider and its suspension during normal operation are relatively rigid, but are somewhat fragile when subjected to tangential forces.
Typically, in these conventional magnetic disks, the slider is biased against the disk surface by a small force from the suspension when the disk is not rotating. The slider is in sliding contact with the disk surface from the time that rotation of the magnetic disk is initiated, until the disk reaches a rotational speed sufficient to cause the slider to ride on the air bearing. The slider also contacts the disk surface when the rotation of the disk is slowed to a stop and the rotational speed of the disk falls below that necessary to create the air bearing.
In such magnetic disks, a lubricant is often maintained on the disk surface to prevent damage to the head and the disk during starting and stopping of the disk. An existing problem with such magnetic disks is that after the slider has been in stationary contact with the disk surface for just a short period of time, the slider tends to resist translational movement or stick to the disk surface. This adherence or "stiction" is known to be caused by a variety of factors, including static friction and viscous shear forces. However, "stiction" is aggravated by the presence of the lubricant material on the disk surface which tends to puddle up between the disk surface and the slider when the disk is not in motion and the slider rests on the disk surface. Even in those magnetic disks which have disks with extremely smooth unlubricated disk surfaces, stiction may occur because of the strong intermolecular attraction at the interface between the smooth disk and slider surfaces. "Stiction" causes severe damage to the head or disk when the slider suddenly breaks free from the disk surface, once disk rotation is initiated. Additionally, as the disk begins rotation, substantial forces, caused by "stiction," can be applied tangentially on the suspension, resulting in damage to or destruction of the suspension and possible damage to the disk surface.
In one known technique to overcome the stiction problem in such rotating disk systems, disk rotation is started very slowly so that the slider gradually breaks free from the disk surface. This approach is undesirable because it requires a relatively long period of time to bring the magnetic disk up to operating speed and additionally imparts tangential forces to the suspensions, which is the direction in which they are structurally weakest. In accordance with another technique, the slider and its suspension structure are moved a slight amount in each disk radial direction, a number of times, prior to applying power to rotate the disks at start up. This controlled micromotion has been found to be effective only in a few cases.
It is recognized that higher magnetic recording density requires correspondingly reduced head-to-disk spacing (flying height). At times, the head-to-disk spacing is so decreased that the magnetic head slider comes into contact with the magnetic disk surface frequently during the starting and stopping operation. Furthermore, the flying height may be so decreased that, even during the flying period, if the magnetic disk has flaws, such as tiny projections or dust on the surface, the magnetic disk may be contacted. Under these circumstances, the reliability of a magnetic recording device greatly depends on the sliding characteristics of the magnetic head slider.
To prolong system life, many approaches to the stiction problem have been proposed Most of the proposals apply impregnation or coating of lubricating materials to the magnetic disk surface and may improve the slidability. However, with the impregnation of the lubricant in the porous voids in the magnetic disk surface, although an improvement in the slidability results, the head still adheres to the recording medium. If an excessively large amount of a liquid lubricant is applied on the top of the magnetic disk, stickiness between the head slider and the surface of the disk may actually increase. Consequently, not only the number and size of the porous voids in the slider must be controlled purposely, but also the viscosity and quantity of the liquid lubricant must be selected. This requires the use of extremely sophisticated manufacturing techniques.
Another approach addresses the stiction problem by scribing minute circumferential grooves on the magnetic disk substrate. However, this method limits maximum recorded densities by increasing media defects and noise production (spacing modulation) and results in increased manufacturing costs.
U.S. Pat. No. 4,549,238 describes a texturing technique for alumina-titanium carbide thin film heads using a CF4 plasma etching process to selectively remove the surface layer titanium carbide particles. The intention of this process is to reduce the effective hardness of the slider instead of reducing stiction, and thereby reduce wear of the disk upon landing and taking off.